1. Technical Field
The present invention relates to an ultrasonic sensor and a measuring method using the same, and a method for manufacturing an ultrasonic sensor.
2. Related Art
Hitherto, an ultrasonic sensor is known as one of a detector for obtaining various information relating to a measuring target. On the basis of the time that is from the time of transmitting an ultrasonic wave until the time of receiving an echo signal which is generated in such a manner that the transmitted ultrasonic wave is reflected on the measuring target and comes back, the ultrasonic sensor obtains the information relating to a position, a shape, and speed of the measuring target.
As an ultrasonic sensor of such kind, for example, an ultrasonic sensor that includes a control calculation section which calculates the position, the shape, and the speed of a detection target (measuring target), on the basis of the ultrasonic wave transmitted from an ultrasonic sensor unit having a vibration plate and a piezoelectric material, and the ultrasonic wave reflected by the detection target and received by the ultrasonic sensor unit, and covers the periphery of the piezoelectric material by a reflection chamber, is known (for example, see JP-A-2010-164331). In addition, as the ultrasonic sensor of such kind, for example, an ultrasonic sensor that includes a support in which an opening section is formed; a support film which is provided to close the opening section; a piezoelectric material (piezoelectric element) which is provided on the side opposite to the support of the support film; and a frame which is provided around the piezoelectric element, and further includes a sealing film sealing the piezoelectric element, in which a space sealed by the sealing film (space including the piezoelectric element) is filled with silicone oil as a pressure medium, and is applied as a pressure sensor, is known (for example, see JP-A-2012-215533 (FIG. 3(B) or the like)).
However, in the ultrasonic sensor of JP-A-2010-164331, there is a case of generating other ultrasonic waves which are transmitted in a different direction from the ultrasonic wave transmitted to the measuring target side. For that reason, with respect to all of the generated ultrasonic waves, there is a case that a ratio of the ultrasonic wave transmitted to the measuring target side becomes low. If the propagation efficiency of the ultrasonic wave transmitted to the measuring target side is not sufficient, there is a possibility that various information relating to the measuring target may not be accurately obtained. In addition, in JP-A-2012-215533 (FIG. 3(B) or the like), since the space including the piezoelectric element is filled with the silicone oil, there is a case of generating a leakage current via the silicone oil during driving of the piezoelectric element. In this case, there is a possibility that it becomes difficult to improve detection accuracy including capability (distance resolution) to separate and identify a measuring target.
Furthermore, such problems are similarly present in not only the ultrasonic sensors of JP-A-2010-164331 and JP-A-2012-215533, but also, for example, the ultrasonic sensor that has the vibration plate and the piezoelectric material, and generates other ultrasonic waves which are transmitted in the different direction from the ultrasonic wave transmitted to the measuring target side.
The present invention is made by considering the above-described situations, and object thereof is to provide an ultrasonic sensor that can improve propagation efficiency of an ultrasonic wave and a measuring method using the same, and a method for manufacturing an ultrasonic sensor.